Keys to Successful Multi-Fractured Horizontal Wells In Tight and Unconventional Reservoirs

Transcription

1 Keys to Successful Multi-Fractured Horizontal Wells In Tight and Unconventional Reservoirs Presented by: Larry K. Britt NSI Fracturing & Britt Rock Mechanics Laboratory

2 Key Questions for Horizontal Success Where Do I Land the Horizontal Well? How Do I Complete The Well? Where Do I Complete The Well? How Many Completions Do I Need? How Do I Fracture Stimulate The Well? What Fracturing Fluid Do I Use? What Pump Rate Should I Use?

3 Key Questions for Horizontal Success Where Do I Land the Horizontal Well? Core How Do I Complete The Well? Permeability/Core Where Do I Complete The Well? Core How Many Completions Do I Need? Permeability How Do I Fracture Stimulate The Well? Core What Fracturing Fluid Do I Use? Permeability/Core What Pump Rate Should I Use? Core * Core Represents Mineralogy, Rock and Geomechanics

4 Keys to Horizontal Success Design For Success Through Petrophysics Ductility (Mineralogy, Rock & Geomechanics) Permeability Completion(s) & Stimulation(s) Fracture Length & Lateral Length Execute, Execute, Execute

5 Presentation Outline Historical Perspective: Horizontal Wells Horizontal Well Characterization & Objectives Basis of Water Frac Designs Ductility Permeability Geomechanics Summary

6 Horizontals: A Historical Perspective 4000 Unconventional SPE Horizontal Well Papers Horizontal Drilling Boom 1998 Only 40 Horizontal Capable Rigs In U.S % Of U.S. Rigs Horizontal Capable % Of U.S. Wells Are Drilled Horizontal First Russia Thermal Cold Lake Year East Texas North Sea 1 st Barnett Austin Chalk Coning, Empire Abo

7 Well Characterization & Objectives Metrics Used To Determine The Optimum Distance Between Fractures/Compleions 1000 Economics 8 Annualized Rate Distance Between Fractures, feet Instantaneous Rate The IP And Annualized Rate Metrics Are Based On The Distance Between Fractures When Interference Occurs At 30 Days Or 365 Days, Respectively Reservoir Permeability, md

8 Well Characterization & Objectives Effect Of Lateral Length On Completion Optimization The Longer The Lateral The More Completions To Be Optimal 4,000 Feet Net Present Value, M$ ,000 Feet 2,000 Feet 1,000 Feet Number of Fractures

9 Well Characterization & Objectives Effect Of Fracture Length On Completion Optimization Net Present Value, M$ The Longer The Fractures The More Completions To Be Optimal 1,500 Feet 1,000 Feet 500 Feet Number of Fractures

10 Well Characterization & Objectives Unconventional Tight Conventional Distance Between Fractures, Feet Control Limited Control No Control Cased & Cemented External Packers Open Hole Reservoir Permeability, md

11 Presentation Outline Historical Perspective: Horizontal Wells Horizontal Well Characterization & Objectives Basis of Water Frac Designs Ductility Permeability Geomechanics Summary

12 Basis of Fracture Design Imperfect Transport Perfect Transport

13 Schematic of a Water-Frac Un - Propped H f H p Un-propped Crack Tests Integrate The Lab Results With The Field & Explains The Effect Of Poor Proppant Coverage!

14 Water Frac Guidelines Must Depend on Un-Propped k F w F CD = Vert ( k k f w ) H Unpropped F Unpropped As Long As F CD-Vert > 2 The Propped Fracture Height Doesn t Matter! For (k f w) Un-propped = 1 mdft H F-Un-propped < 50 feet

15 Why Un-Propped Crack Testing? With Un-Propped k f w A Shale Reservoir Can Support Hundreds Of Feet Of Un-Propped Fracture! This Is Why Water-Fracs Should Only Be Applied To Tight Unconventional Reservoirs & Proppant Is Always Needed!

16 Water-Frac s Must Depend On Un-Propped Fracture Conductivity MCFPD Water Fracs Gel Fracs "Normalized" Production Data Area 4,5, & 7 Represents Woodlawn & Blocker Fields Where Taylor (CV) Sand Is 100+ Feet Thick! Area 1 Area 2 Area 3 Area 4 Area 5 Area 6 Area 7 Area 8

17 Mineralogy & Ductility Proppant And Fluid Selection & Quantity: Mineralogy Quartz Clay Constituents Less Than 40% Minimal Swelling Clays (Smectite) Quartz Clay Carbonate Carbonate Clay

18 Young s Modulus & Brittleness Proppant And Fluid Selection & Quantity: Young s Modulus Young s Modulus > 3.5 x 10 6 psi Fits Clastic Modulus Correlation

19 Un-Propped Crack Test & Ductility Proppant And Fluid Selection & Quantity: Un-Propped Crack Conductivity e *x e *x Best Shale Plays Maintains Un-Propped Conductivity Fits Within Acceptable Range Normalized k Marginal Shale Plays Normalized Stress

20 Basis of Fracture Design Imperfect Transport Perfect Transport

21 Water Frac Design Example Minimal Required Proppant, lbs Fluid Viscosity, 1 cp Frac Height, /70 Ottawa Sand Barnett Design: 25 BPM 100 BPM Static Young s Modulus, x 10 6 psi Young s Modulus 4 x 10 6 psi 25 BPM Need 35 mlbs 50 BPM Need 40 mlbs 100 BPM Need 45 mlbs 50 BPM

22 Water Frac Design Example Barnett Design: Young s Modulus 4 x 10 6 psi 0.25 PPG Need 250 mgals 0.50 PPG Need 110 mgals 1.00 PPG Need 60 mgals Minimum Fluid Requirement Does Not Consider Dilation!

23 Presentation Outline Historical Perspective: Horizontal Wells Horizontal Well Characterization & Objectives Basis of Water Frac Designs Ductility Permeability Geomechanics Summary

24 Post Fracture Decline Analysis Example 2940 Stress (psi) Static Mod (MMpsi) 3999 MD m Logistical & Material Sourcing Issues Required An Extended Shut Down: So We Monitored Pressure Decline! TVD (m) Shale Gas Shale Stage 6 Stage 4 Stage Silty Stage 5 Stage 3 Stage GR API Static Mod MMpsi Dy n PR unitless C 16-6 shear US/M Dyn E MMpsi DT35 US/M Stress psi DPRS PERC NPRS PERC Pcl (kpa) 0 E 7 (MMpsi) Loss Coefficient (ft/sqrt(min))

25 Post Fracture Decline Analysis Example Calc BHP(kPa) Blessed Pc Tc 0.57 EFFc 0.59 Isip dps Blessed Pc Tc 5.28 EFFc 0.86 Isip dps dp/d[sqrt(dt)] Isip Used The Shut Down To Make Real Time Completion & Stimulation Decisions! sqrt(dt)

26 dp Post Fracture Decline Analysis Example Tp Mp (kpa) Kh/mu kh (md-ft) k (md) Mp/Dp 20 (kpa) dt Fissure Enhanced Loss Type Curve Analysis Indicates A Permeability Of md! Enter up to 5 Tp values for different Type curves Auto-Select dp' Type Curve Analysis Of Post Fracture Pressure Decline! ACA Regimes Plot /F-L^2 dp' Tp =.001 Tp =.005 Tp =.01 Tp =.05 Tp =.1 dp'

27 Post Fracture Decline Analysis Example xf = 160 m & kfw = 1479 mdft (Shortest Of Six Stages) Gas Productivity, Mscfpd Average Fracture Dimensions xf= 223 m & kfw = 935 mdft (Average Of Six Stages) x f =600 ft, k f w =1,000 mdft xf = 270 m & kfw = 692 mdft (Longest Of Six Stages) Average Dimensions Of Six Stages: IP(30 days) = 4.3 mmcfpd IP Increased With Fracture Conductivity Reserves Increased With Fracture Length Cumulative Gas Over Five Years, MMCF

28 Presentation Outline Historical Perspective: Horizontal Wells Horizontal Well Characterization & Objectives Basis of Water Frac Designs Ductility Permeability Geomechanics Summary

29 Geomechanics of Horizontal Wells σ v = 10,000 psi, σ Hmax = 7,500 psi, σ Hmin =6,000 psi β = 90 o α = 0 o, BD = 4,000 psi α = 30 o, BD = 4,154 psi α = 60 o, BD = 5,574 psi α = 90 o, BD = 8,500 psi

30 Geomechanical Implications Width / Width Single Fracture Two Fractures dx / H Two Interfering Fractures w/ Contained Fracture Geometry dx H Flow Resistance Slide Keys: When The Distance Between The Fractures Is > 2 Times The Fracture Height Minimal Effect On Fracture Width & Flow Resistance! dx / H

31 Geomechanical Implications What Is The Likely Fissure Direction In The Current Stress State Whereby: The Natural Fissures Are Open, The Fissures Are Conductive, And Potentially Contributory To Well Performance µ µ Such A Natural Fissure Is Deemed Critically Stressed

32 Geomechanical Implications The Object Of The Completion(s) & Fracture Stimulation(s) Is To Effectively Contact As Much Reservoir As Possible: Micro-Seismic Data Used To Assess Contacted Volume Or Stimulated Reservoir Volume Where: SRV = L x H x W of Micro-Seismic Event Map Often 2(x f ) x H f x L L

33 Geomechanical Implications Stimulated Reservoir Volume Bigger The Frac Volume The Greater The Stimulated Reservoir Volume & The Greater The Hydrocarbon Recovery Fisher 2002

34 Geomechanical Implications If SRV Important How Do You Get More? Study Showed That Higher Fluid Viscosity Slightly Increased The Tensile Failure Area Study Showed That Low Fluid Viscosity Dramatically Increased The Shear Failure Sanchez-Nagel

35 Geomechanical Implications But Does Complexity Or Stimulated Reservoir Volume Add Up To Hydrocarbon Recovery Study Showed That SRV Not Very Effective, Neither Was Induced Fracture For That Matter Additional Simulations Show That SRV May Not Be Critical Or Is It? What About Over The Long Term? Britt, No Fracture Network 8 Induced Fractures w/ 100 md-ft Britt, No Fracture Network 6 Induced Fractures w/ 100 md-ft Cipolla

36 Keys to Horizontal Success Design For Success Through Petrophysics Ductility (Mineralogy, Rock & Geomechanics) Permeability Completion(s) & Stimulation(s) Fracture Length & Lateral Length Execute, Execute, Execute